The U.S. Army uses a turret motion base simulator to move a turret detached from its armored vehicle as if the turret were actually on the vehicle during travel over various terrains. To install a turret on the simulator, it is necessary to have a work platform at the testing station disposed at the height of the turret. The platform needs an access stairway so that workmen carrying tool boxes or test equipment can get to the platform from the ground. Since the U.S. Army tests turrets of varying configurations, it is helpful and often necessary to raise and lower the platform to better adapt the platform to a given turret. Consequently, the U.S. Army needs a stairway that moves with the platform but still allows workmen to carry heavy or bulky objects between the ground and the platform.
I have devised an adjustable stairway which can both rise with the platform and form either an inclined or a horizontal ramp suitable for wheeled carts. My stairway comprises two parallel upper frame members swingable about a first axis and two parallel lower frame members swingable about a second axis. A set of horizontal steps are pivotally connected to the frame members and normally remain parallel as the stairway swing up and down about the axes. When the frame members reach a horizontal position, the stairway is collapsed such that the steps are aligned in a common plane to form a runway. The connection between the base and the upper frame members can be released so that the steps can be swung into the common plane when the frame members are not horizontal, whereby the stairway forms an inclined ramp.